Winding arrangement in alternating current machines



June 14, 1949. s .GYNT 2,473,144-

WINDINGv ARRANGEMENT IN ALTERNATING CURRENT MACHINES Filed July 2j 1947Patented June 14, 1949 WINDING ARRANGEMENT IN ALTERNATING CURRENTMACHINES Sven Gynt, Vasteras, Sweden, assignor to Allmanna SvenskaElektriska Aktebolaget, Vasteras, Sweden, a corporation of SwedenApplication lluly 2, 1947, Serial No. 758,645 In Sweden July 8, 1946 4Claims. 1

In large electrical generators and other alternating current machines,the voltage induced in the different strands in the slots will bedifferent due to the fact that the magnetic eld acting on the strands inthe slot will not be the same al-ong the whole depth of the slot. Iftherefore, in a generator, the circuit has a plurality of parallelcoupled strands, there will be an equalisation current between thestrands, if the voltage induced in the different strands were notequalized thereby that the strands were transposed from slot to slot, sothat the mean position in relation to the slots will be the same orpractically the same for all parallel-connected strands. As, however, ina slot and the end windings belonging to the slot there is a certainvoltage diierence between the different strands it is necessary toinsulate them from each other. If by some reason this insulation shouldbe faulty there occurs equalisation currents between the strands, whichQ currents can get considerable values. In order to detect such faultspreviously used method has been to connect the strands when they leavethe machine into two groups, so that one group has contained alternatestrands and the other group z the strands between them, and the currentsfrom these groups have in opposite direction been conducted each throughits own primary winding of a current transformer with two primarywindings or through the primary winding of separate current transformersdifferentially coupled. The secondary winding or secondary windingsrespectively have then been connected with an indicating device. Theequalisation current caused by a fault in the insulation has in thismanner been possible to indicate or to be measured, and by this deviceit has also been possible to detect a break of the strands.

The present invention has for its object an improvement of the knownarrangement and is characterized thereby that the currents coming fromthe two groups of the strands of the machine in one or both ends of eachphase in opposite directions traverse a reactor, which Imay be providedwith a secondary winding with a high resistance, to which winding arelay or also a voltmeter may be connected. By this arrangement theadvantage is gained that not only a fault in the insulation or a breakin a part is indicated but also that a limitation of the equalsationcurrent caused by the fault in the insulation is obtained.

On the accompanying drawing a form of the invention is schematicallyshown, where I-S designate the strands of the machine located in n l oi) (Cl. Ill- 252) the slots 'I-|2. The parts of the strands within theslots are designated by thick lines, whereas the connections betweenthem outside of the slots are designated by ne lines. In each end of thewinding the strands are assembled, so that 1n one end the strands I 3and 5 are joined with each other and by means of conductors I3 and |31which traverse the cores I4 and |41 of reactors I5 and |51 respectivelyat the end points of the winding before they are connected with theneutral point of the machine or its terminal. The strands 2, 4 and 6 arein the same manner joined with each other and with conductors IE and|61, which also traverse through the cores I4 and |41 before they arejoined with the neutral point or terminal of the machine, but theseconductors traverse the cores I4 and |41 in a direction opposite to theconductors I3 and |31. On the cores I4 and |41 also secondary windingsI'I and |11 are arranged, which have a comparatively high resistance,and which by means of switches I8 and |81 may be connected either withdisconnecting tripping relays I9 and |91 or voltmeters 20 and 201.

As under normal conditions, the voltage induced in the different strandswill be the same or practically the same, the currents through theconductors I3 and I6 will be equal and as they traverse the core I4 inopposite directions, they are not able to induce any field in this core,and the same will be the conditions in the reactor |51. If, however, afault should occur for instance in the point 2| between the strand I andthe strand 6, it is evident that due to the difference of the voltagesinduced in strand and strand 6 in slot 'I, a circulating current occurs,for instance as shown by the arrows on the drawing, and in the samemanner due to the diiierence between the induced voltages of the strandsI and 6 in the other slots, there occurs a circulating current throughthe conductors |31 and |61. Due to the action of the reactors I 5 and|51, these currents, however, will be reduced to a small fraction of thevalue they should have, if the reactors I5 and |51 should be omitted orshould be normal current transformers.

In certain cases, each phase consists of a plurality ofparallel-connected circuits, each containing a plurality of strands.Also in this case, the invention can be applied thereby that eachseparate circuit is provided with reactors or thereby that the strandsfrom the diierent circuits are joined and the strands thus joined inabove described manner are connected into groups for the connection tothe windings of the reactors. In the same manner it is possible in astar-connected winding or in delta-coupled machines first to join thestrands from the diiierent phases before they are assembled to groupsconnected to the conductors through the reactors and thus before allparts are joined in the neutral point or at the terminal.

In the part of the description belonging to the attached drawing, it issupposed that each slot contains only one conductor. It is, however,obvious that the invention also is applicable in the case that the slotcontains a plurality of conductors. The strand transposition shown isalso only shown as an example and can be made in other manners betweenthe different slots and also in the slots themselves.

I claim as my invention:

1. Arrangement in electric alternating current machines, comprisingwindings With conductors having a plurality of strands which changetheir relative `positions in the slots of the machine when proceedingfrom one slot to another, a reactor at each end of the said windings,two opposing reactor windings, a connection between alternate strands inthe winding of the machine and one end of one reactor winding, aconnection between the remaining strands of the winding of the machineand one end of the other reactor' winding, and means coupling the otherends of the reactor windings.

2. Arrangement in electric alternating current machines, comprising aplurality of windings each divided into a plurality of circuits, theconductor of each circuit consisting of a plurality of strands whichcha-nge their relative positions in the slots of the machine whenproceeding from one slot to another, a reactor at each end of the saidwindings, two opposing reactor windings, alternate strands of thecircuits being connected with one end of one of the reactor windings,the remaining strands of the circuits being connected with one end ofthe other reactor winding, and means connecting the other ends of thereactor windings.

3. Arrangement in electric alternating current star-connected machines,comprising a multiphase winding with conductors having a plurality ofstrands which change their relative positions 4 in the slots of themachine when proceeding from one slot to another, a reactor at eachterminal of the machine, a reactor at the star point of the winding,said reactors being provided with two opposing windings, alternatestrands of the conductors at the terminals being joined with one end ofone winding of the reactor, the remaining strands being joined with oneend of the other winding of the reactor and at the star point of thewinding, corresponding strands of the phases being joined by an equalnumber of conductors, alternate conductors being joined with one end ofone winding of the reactor, the remaining conductors being joined withone end of the other winding of the reactor, and the other end of thereactor windings being connected together and with the star point.

4. Arrangement in electric alternating current delta-connected machines,comprising a multiphase winding with the conductors having a pluralityof strands which change their relative positions in the slots of .themachine when proceeding from one slot to another, a reactor at eachterminal of the machine, said reactors being provided with two opposingwindings, alternate strands of the conductors at the terminals beingjoined with one end of one winding of the reactor, the remaining strandsbeing joined with one end of the other winding of the reactor and at theterminals of the machine, corresponding strands of the phases beingjoined by an equal number of conductors, alternate conductors beingjoined with one end of one winding of the reactor, the remainingconductors being joined with one end of the other winding of thereactor, and the other end of the reactor windings being connectedtogether and with the terminals of the machine.

SVEN GYNT.

REFERENCES CITED UNITED STATES PATENTS Name Date Perry et al Dec. 27,1932 Number

